The present invention relates to spray-dried detergent compositions comprising a nonionic surfactant which is intimately associated with a kaolinite or bentonite clay, and processes for preparing same. The use of kaolinite or bentonite clay in a detergent crutcher mix, in the manner disclosed hereinafter, provides a homogeneous, non-oily mix which can be conveniently spray dried. Detergent granules spray dried from crutcher mixes prepared in the manner of this invention have improved properties over spray-dried detergent granules containing nonionic surfactants heretofore known.
In the preparation of spray-dried detergent granules an aqueous mixture of the various components of the granules (the crutcher mix) is sprayed or otherwise introduced into what is essentially a drying tower. As the droplets of the crutcher mix proceed through the drying tower, the water is flashed off and solid or semi-porous detergent granules are secured. The advantage of spray-dried detergent granules over granules obtained by simple dry mixing of the individual ingredients is their homogeneity. That is to say, each granule contains the various ingredients in the same ratios and proportions introduced into the original crutcher mix. This provides obvious advantages over simple dry-mixed detergent formulations, inasmuch as dry mixing can result in inhomogeneity in the final detergent formulation such that the user is never certain of the composition of any given portion of such products.
In order to provide a homogeneous spray-dried granule it is necessary that the crutcher mix, itself, be substantially homogeneous. In some instances, a crutcher mix may be a homogeneous solution. However, in order to provide a crutcher solution, excessive amounts of water are needed to dissolve all the components. Use of excessive amounts of water requires additional drying capacity in the spray-dry tower and is not economically attractive. For the most part, the cructher mixes employed in the preparation of spray-dried detergent compositions are semi-dissolved aqueous slurries of the various components desired in the final spray-dried granules. This causes problems in maintaining the homogeneity of such mixes.
The introduction of alkoxylated nonionic surfactants into an aqueous detergent crutcher mix adds a new dimension to the problems encountered with maintaining a relatively homogeneous mixture. Nonionic surfactants tend to be oily and exist as a separate phase within the crutcher mix. Such non-homogeneity in the crutcher mix is intolerable when preparing a homogeneous spray-dried detergent granule. Of course, the separation problem is accentuated by the increased amounts of nonionics used in modern detergent compositions.
A variety of methods have heretofore been employed to provide the requisite homogeneity of crutcher mixes containing nonionic surfactants. Perhaps the most widely used method involves the addition of certain alkyl phosphate esters to the crutcher mix. While the exact mechanism is not known, the phosphate esters appear to "couple" the nonionic to the other components of the mix, thereby providing the requisite homogeneity.
The use of phosphate esters in crutcher mixes is not without its drawbacks. While effective for the intended puspose, the phosphate esters tend to leave a residual greasy feel on the surface of the spray-dried granules. Moreover, the introduction of phosphorus in a detergent composition, in any form, may be undesirable when such detergent compositions are used in areas of the country having incompletely treated sewage. Accordingly, it is desirable to provide an alternate method for securing a substantially homogeneous crutcher mix containing relatively large amounts of nonionic surfactants.
It has now been found that kaolinite and bentonite clays, when employed in combination with an alkoxylated nonionic surfactant in the manner hereinafter disclosed, provide stable, homogeneous crutcher mixes. Such stabilized crutcher mixes do not experience separation of an oily phase comprising the nonionic surfactant. Moreover, the spray-dried detergent granules prepared from the crutcher mixes herein have unexpected advantages over other spray-dried granules containing nonionic surfactants, but without added kaolinite or bentonite clays.
The use of clays in detergent compositions for a variety of purposes is well known; see, for example, U.S. Pat. Nos. 2,118,310; 2,205,021; 2,296,639; 2,344,268; 2,491,051; German Pat. No. 361,520; and British Pat. Nos. 469,344; and 579,835.
More particularly, Schwartz, Perry and Birch, "Surface Active Agents and Detergents" Vol. II, Interscience Publishers, Inc., 1958 at page 299, broadly teach that clays have been used to sorb the normally liquid nonionic detergents used in powdered household detergent formulations. U.S. Pat. Nos. 2,594,257 and 2,594,258 specifically relate to the sorption of nonionic surfactants of various types on sorbents such as kieselguhr and attapulgite, and the use of such compositions in dry-mixed detergent compositions. The sorbed nonionics are taught not to "bleed" from such compositions.
The prior art teachings regarding the use of clay to sorb nonionic surfactants in detergent compositions are useful for formulating dry mixtures, but the use of clays to provide homogeneous crutcher mixes suitable in spray-drying processes has not been disclosed heretofore.
Moreover, the problem of heterogeneous crutcher mixes is not solved by a random selection of sorbent clay carriers for the nonionics. The water and alkalinity of the crutcher mix tend to displace the nonionics from most carrier materials, resulting in phase separation. Other surfactants which may be present in the crutcher mix, especially the anionics, aid in this displacement and add to the problem.
In contrast with other clays, the kaolinite and bentonite employed as a sorbent carrier for nonionic surfactants in the particular manner disclosed hereinafter provide a stable, homogeneous crutcher mix. This is especially surprising with kaolinite since this clay is not recognized as being a useful adjuvant with most nonionic surfactants in aqueous media and, hence, is not generally used in combination therewith.
In addition, it has been found that the spray-dried detergent granules prepared in the manner disclosed herein have desirable properties over spray-dried granules containing nonionic surfactants heretofore prepared.
It is an object of this invention to provide homogeneous crutcher mixes containing substantial quantities of nonionic surfactants without the need for phosphate ester couplers.
It is another object herein to provide improved spray-dried detergent granules containing kaolinite or bentonite clay and substantial quantities of nonionic surfactants, and improved processes for preparing same.
These and other objects are obtained herein as will be seen by the following disclosure.